Asteroids, Comets and Asteroids, News

Rings Discovered Around an Asteroid

Posted by Jason Major on
Artist's impression of the view from the asteroid Chariklo. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)
Artist’s impression of the view from the asteroid Chariklo. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)

We all know that Saturn is encircled by a system of rings, and perhaps you also know about the fainter rings around Uranus, Jupiter, and Neptune. But today, ESO astronomers have revealed a surprising discovery: there are also rings surrounding the asteroid 10199 Chariklo, a small, distant world orbiting the Sun far beyond Saturn.

This makes 250-km-wide Chariklo the fifth world ever found to have rings, after the four planets mentioned previously, and, based on the observations, it could also even have its own moon.

“As well as the rings, it’s likely that Chariklo has at least one small moon still waiting to be discovered,” said Felipe Braga-Ribas of the Observatório Nacional/MCTI in Rio de Janeiro who planned the observation campaign and is lead author on the new paper.


From an ESO news release:

Chariklo is the largest member of a class known as the Centaurs and it orbits between Saturn and Uranus in the outer Solar System. Predictions had shown that it would pass in front of the star UCAC4 248-108672 on June 3, 2013, as seen from South America. Astronomers using telescopes at seven different locations, including the 1.54-meter Danish and TRAPPIST telescopes at ESO’s La Silla Observatory in Chile, were able to watch the star as its light was briefly blocked by Chariklo.

Watch a video of the occultation below:

They found much more than they were expecting. A few seconds before, and again a few seconds after the main occultation, there were two further very short dips in the star’s apparent brightness. Something around Chariklo was blocking the light! By comparing what was seen from different sites the team could reconstruct not only the shape and size of the object itself but also the shape, width, orientation and other properties of the newly discovered rings.

The team found that the ring system consists of two sharply confined rings only seven and three kilometers wide, separated by a clear gap of nine kilometers.

Artist's impression of Chariklo and its rings. Credit: Choose your language: Artist’s impression close-up of the rings around Chariklo Artist’s impression close-up of the rings around Chariklo Click to Enlarge Observations at many sites in South America, including ESO’s La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. This is the smallest object by far found to have rings and only the fifth body in the Solar System — after the much larger planets Jupiter, Saturn, Uranus and Neptune — to have this feature. The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris. This artist’s impression shows a close-up of what the rings might look like. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)
Artist’s impression of Chariklo and its rings. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)

“We weren’t looking for a ring and didn’t think small bodies like Chariklo had them at all, so the discovery — and the amazing amount of detail we saw in the system — came as a complete surprise!”
– Felipe Braga-Ribas, Observatório Nacional/MCTI

The results were published online in the journal Nature on March 26, 2014.

Read the full ESO press release here.

UPDATE: A year after these findings were published, another centaur was found to possibly possess a ring system — the 136-mile (220-km) minor planet Chiron. But, known to also exhibit comet-like behavior, Chiron’s “ring” could also be part of its jetting activity. Read the news from MIT here.